The International Classification of Diseases 2010 (ICD-10) defines stuttering, which is also called stammering, as “[s]peech that is characterized by frequent repetition or prolongation of sounds or syllables or words, or by frequent hesitations or pauses that disrupt the rhythmic flow of speech.” Stuttering is classified as a disorder when it markedly disturbs the fluency of speech. Typically, the disorder includes repeated articulatory movements (e.g., t-t-t-talk) and/or fixed articulatory movements (e.g., mmm-mine). Verbal interjections (e.g., “um” or “like”) are common. Verbal signs can be accompanied by nonverbal signs, including facial grimaces, excessive eye blinking, muscle tension, odd movements of the head, and struggling to speak. These behaviors may be learned approaches to minimize the severity of a stutter. People who stutter often experience emotional distress, and anxiety can cause them to avoid educational and social situations that they would otherwise enjoy and benefit from.
The neurophysiological basis of stuttering is thought to share some similarities with other movement disorders. Specifically, stuttering may arise due to abnormal signaling in one or more of the circuits between the cortex, striatum, globus pallidus, and thalamus (the cortical-striatal-pallidal-thalamo or CSPT circuit). Circuit models have implied that excess dopamine activation increases unwanted movements of the muscles controlling speech (at D1 receptors) and, conversely, that dopamine blockade (at D2 receptors) promotes unwanted movements. Known D2 antagonists like clozapine, olanzapine, asenapine, and risperidone have all been reported to induce stuttering (Grover et al., 2012; Bar et al., 2004; Yaday, 2010; Maguire et al., 2011) and D2-preferring dopamine agonists such as methylphenidate have been reported to relieve stuttering (Devroey et al., 2012).
We are unaware of any treatments approved by any recognized government regulatory authority for the treatment of stuttering. Most patients are treated with behavioral techniques (see Blomgren, Psychol. Res. Behay. Management, 6:9-19, 2013). When used in severely afflicted patients, pharmacotherapy typically involves drugs for the treatment of anxiety (see, e.g., Maguire et al., J. Clin. Psychopharmacol. 30:48-56, 2010). This is based on the observation that stress exacerbates stuttering and the assumption that reducing stress will relieve some symptoms.
Several review articles concerning stuttering are available. These include: Boyd et al., J. Clin. Psychopharmacol., 31:740-744, 2011; Ingham, et al., J. Fluency Disord., 28:297-317, 2003; Maguire et al., Expert Opin. Pharmacother., 5:1565-1571, 2004; Kraft and Yairi, Folia Phoniatrica et Logopaedica, 64:34-47; Ashert and Wasson, Journal of American Osteopathic Association, 111:576-580; Newbury and Monaco, Neuron, 68:309-320; Prasse and Kikano, American Family Physician, 77:1271-1276, 2008; Büchel and Sommer, PLoS Biology, 2:159-163; Bothe et al., American Journal of Speech-Language Pathology, 15:321-341, 2005; Costa and Kroll, Canadian Medical Association Journal, 162:1849-1855, 2000; and Ashert and Wasson, Journal of American Osteopathic Association, 111:576-580, 2011).